﻿using System;
using System.Linq;

class FiveDivision
{
    static void Main (string[] args)
    {
        //Read numbers from console
        string input = Console.ReadLine ();
        int integer1 = int.Parse (input);

        input = Console.ReadLine ();
        int integer2 = int.Parse (input);

        // Swap integers if first integer is greater
        if (integer1 > integer2)
        {
            int temp = integer1;
            integer1 = integer2;
            integer2 = temp;
        }

        // Count numbers
        int numbersCount = 0;
        for (long i = integer1; i <= integer2; i++)
        {
            if (i % 5 == 0)
            {
                numbersCount++;
            }
        }
        // Print result 
        Console.WriteLine (numbersCount);
    }
}
